<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        iframe {
            width: 500px;
            height: 400px;
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>
    <a href="./red.html" target="main_frame">红色的页面</a>
    <a href="./green.html" target="main_frame">绿色的页面</a>
    <a href="./blue.html" target="main_frame">蓝色的页面</a>
    <hr>
    <!-- 利用一个新标签来作为页面的容器 -->
    <iframe src="./red.html" name="main_frame"></iframe>
</body>
</html>